Apparatus and method for producing small gas bubbles in liquids

ABSTRACT

An apparatus for creating microbubbles of gas in a liquid. A vertical pipe member is adapted to receive a liquid-gas mixture having gas bubbles of larger diameter therein. A series of horizontally-extending apertures are provided to permit the pipe member to expel such liquid-gas mixture radially outwardly from such pipe member. The expelled liquid-gas mixture may contact the sides of a containment vessel. In a refinement of the invention, a specific relationship is further specified between the exit area of the apertures and the interior cross-sectional area of the pipe member, in order to most suitably convert the gas bubbles in such liquid-gas mixture to microbubbles of a desired small size when expelled under pressure from such pipe member via such apertures. A method of converting gas bubbles in such liquid-gas mixture to gas microbubbles is further disclosed.

RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 10/795,239 filed Mar.9, 2004, published as US 2005/0040548A1, claiming priority from CA2,437,948 filed Aug. 21, 2003 and CA 2,460,123 filed Mar. 8, 2004, andis directed inter alia to subject matter of claims 2-4, 7-38, & 43-62 ofpublication US 2005/0040548A1, and is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for aerationand purification of liquids, and more particularly to an apparatus andmethod for producing small gas bubbles in liquids for purification andaeration of said liquids.

BACKGROUND OF THE INVENTION

Entrainment of a gas in a liquid is required in numerous industrialprocesses, typically for the purposes of reacting the gas with suchliquid or materials in such liquid, such as dissolved ions or finelydispersed solids, to cause reaction of such gas with materials thereinto cause same to be neutralized by, react with, or precipitate or befiltered out of such liquid.

For example, it is known to bubble ozone through water, to allow theozone to react and combine with dissolved minerals and/or finelydispersed solids within the water, so as to form solid products whichmay either precipitate out of the liquid or be filtered from the water,so as to thereby purify the water. The ozone may further react withharmful bacteria or the like in the water so as to render them harmlessor odourless.

Where a gas is desired to react with a liquid or finely dispersed solidsin such liquids, it is widely known that small bubbles of gas immersedin such liquid will have, for the same volume of gas, a greater surfacearea and thus a greater liquid/gas interface, than the same volume ofgas when such gas exists in larger bubbles.

A large gas/liquid interface is a desirable characteristic in instanceswhere the gas is introduced into a liquid for the purposes of reactingthe gas with the liquid or dispersed solids in such liquid, sincegreater surface area of the gas exposed to such liquid and/or finelydispersed solids in such liquid decreases the time it takes for the gasto react with the liquid or finely dispersed solids within such liquids,thus allowing quicker processing. As well, a lesser amount of gas, andsmaller containment vessels, can thus be used, resulting in costsavings.

The benefits, therefore, of introducing or entraining very small bubblesof gas, typically in the range of 50 to 100 microns in diameter, into aliquid for the purposes of increasing the surface area of the gasrelative to the liquid (and/or finely dispersed solids in such liquid)are known. Small bubbles of this size are generally referred to in theart as microbubbles. For the purposes hereinafter of this disclosure,microbubbles will be referred to and will be understood as meaning gasbubbles of a diameter in the range of 50 to 100 microns, and preferably5 to 50 microns.

A number of devices and methods for aerating liquids, typically water,with gas bubbles, are known.

For example, U.S. Pat. No. 2,890,838 teaches a device forfilter-separating iron from water. Water is delivered via a pipe 13 toan air aspirator 14, and thereafter such water having air entrainedtherein is delivered via pipe 16 to the upper portion of a tank 10,where it passes vertically downwardly in the tank 10 to a spray valve19. At the spray valve 19 the water-air mixture flows outwardly throughopenings 21 into chamber 22 formed in a cylindrical hollow body 23mounted on valve 19. The upper end of the body 23 is cone shaped, andcontacts the mating lower cone-shaped end 25 of valve body 26. Thewater-air mixture flows upwardly and outwardly through the cone-shapedopening formed between cone-shaped surfaces 24,25 in the form of avaporized spray S, as shown in FIGS. 2 & 4 thereof, and mixes with theair in the tank 10 as it strikes the underside 27 of the top 28 of thetank 10, thereby introducing air into the liquid which in turn oxidizesmetabolic iron present in the water. Iron precipitates then settles outof solution and down through the water contained in tank 10.

U.S. Pat. No. 5,601,724 and U.S. Pat. No. 5,460,731 teach an apparatusand method, respectively of aerating liquids. FIGS. 1 & 2 of each of'724 and '731 show a venturi air injector 10 used to inject air intowater in a conduit 12. Such air-water mixture enters the bottom portionof a tower-like pressure vessel 14, where it is directed upwardly viaconduit 30, where it is directed through a cylindrical restriction gap19 formed between the second end 34 of conduit 30 and the top 18 ofvessel 14. The gas, being of lesser density, passes more quickly throughthe restriction, thereby accelerating the liquid. As the liquid exitsthe restriction gap 19 it pneumatically hammers against the top 18 ofpressure vessel 14. Thereafter the liquid stream, by force of gravity,cascades through the gas in pressure vessel 14 downwardly to furtherimpact plate 35. Thereafter the liquid stream then passes throughopenings 37 in plate 35 and by force of gravity cascades through the gasin pressure vessel 14 to further impact on liquid at the bottom of thevessel. Thereafter such liquid, having small bubbles of air entrainedtherein, is removed via a conduit from the bottom of vessel 14.

U.S. Pat. No. 5,096,596 to a “Process and Apparatus for Removal ofMineral Contaminants from Water” teaches a pressurized aeration tank 24having a tube 26 located within said tank 24 which supplies the tank 24with raw water, which is introduced to the tank 24 via the tube 26 via aplurality of holes 28 in the tube (ref col. 2, lines 49-54 and FIGS.1-7). The tube 24 only supplies “raw water” and not water having airbubbles entrained therein, and is not for the purpose of providing gasmicrobubbles of a range of 5-50 microns. Most importantly, norelationship regarding the size of the holes 28 in the tube 24 isspecified to attempt to attain microbubbles, even if the patent furtherprovided for the raw water to first have bubbles introduced therein.

U.S. Pat. No. 4,556,523 teaches a microbubble injector usable toseparate material of different density by flotation, whereinmicrobubbles of gas are introduced into a chamber 14 containing a liquidmass 16. As may be seen from FIG. 1 of US '523, a gas admixture device 4receives air through an inlet 6 and ordinary water through an inlet 8.The resulting air-water mixture is supplied by a conduit to the bottomof chamber 14, where it passes through an injector wall 10 via aninjector hole 12 to procure a high velocity jet of air water. Adeflector wall 18 is disposed over such injector hole, so as to create anarrow gap around the injector hole, which the water/air mixture mustpass through. The injector hole is preferably substantially circular,and the height of the passage between the injector and deflector wall atthe edge of the injector hole is less than one quarter of the diameterof the injector hole in the injector wall.

Disadvantageously, none of the aforementioned patents teach or discloseany specific design interrelation between the dimensions of the injectorholes/parts/or gaps and the conduit outer dimensions which will bestproduce microbubbles in the liquid

For example, US '838 simply provides a nut 23 on the end of the valve 24to adjust the size of the aperture between cone surfaces 24,25 throughwhich the water must pass. No gap dimension is ever specified which bestprovides bubbles of a desired small size.

Similarly, each of US '724 and '731 simply disclose that the size of therestriction gap 19 required is dependent upon the size of the bubblesthat are produced, with no direction as to what gap size will producemicrobubbles in the range of less than 100 microns. These two patentseach go on to note that (at col. 6, lines 44 to 47) that the greater thediameter of the cylindrical edge, the closer the end of conduit 30 hadto be positioned to the top 18 of the pressure vessel 14 (i.e. thesmaller the restriction gap had to be) in order to form bubbles of thedesired size. No desired size of bubbles was ever identified, nor wasthere ever any relationship specified between the gap size and thediameter of the pipe, which would produce the smallest bubbles, namelymicrobubbles of diameter in the 5-100 micron range.

U.S. Pat. No. 4,556,523 perhaps comes closest to specifying aninterrelation between the components in order to achieve desired smallmicrobubble size in the range of 50 to 100 microns, specifying as notedabove that the passage between the injector and deflector wall at theedge of the injector hole is less than one quarter of the diameter ofthe injector hole in the injector wall. No specific optimum size wasspecified Moreover, the particular manner by which the microbubbles arecreated, namely requiring an injector wall 10 and deflector wall 14,requires substantial quantity of material, and is thus a particularlymaterial-intensive design and thus relatively costly.

Accordingly, a clear and real need exists for an aeration apparatus ofsimple and relatively inexpensive design having a configuration whereinthe size of the flow aperture(s) through which a gas/liquid mixtureflows can be accurately designed so as to give microbubbles of thedesired small size.

SUMMARY OF THE INVENTION

In order to meet the above need for a device of simple and relativelyinexpensive design able to introduce gas microbubbles into a liquid, ina broad aspect of the present invention such invention comprises anapparatus having means for creating microbubbles in a liquid,comprising:

means for introducing gas bubbles, the majority of which are of a sizegreater than 100 microns, into a liquid to from a liquid-gas mixture;

elongate, hollow pipe means, substantially symmetrical in cross-sectionof interior cross-sectional area, positioned substantially vertically,adapted to receive said liquid-gas mixture under first pressure andsupply said liquid-gas mixture to aperture means, said pipe memberhaving plug means situate at a lowermost distal end thereof forpreventing egress of liquid vertically downward from said distal end;

said aperture means situate on said pipe means and disposed in one ormore planes each substantially perpendicular to a longitudinal axis ofsaid pipe means and extending from an interior of said pipe means to anexterior of said pipe means, each adapted to direct said liquidsubstantially horizontally outwardly from said pipe means; and

a containment vessel, to capture said liquid-gas mixture havingmicrobubbles of gas entrained therein.

Importantly, however, and quite surprisingly, it has been furtherdiscovered that for an apparatus of the above design, that in the caseof a pipe member that has a symmetric cross-sectional area and a uniformpipe wall thickness, and a maximum interior width Di and a maximumexterior width Do, a specific inter-relation need exist between theaperture exit area A_(e) of the aperture(s), and the interiorcross-sectional area A_(i) of the pipe means, in order to achievecreation of microbubbles of the desired small size, namely in the rangeof 50-100 microns and preferably in the range of 5-50 microns.

Accordingly, in a highly preferred embodiment, where the aperture meansconsists of at least two apertures, the pipe means is symmetric and hassubstantially identical moments of intertia about two axis in a plane ofcross-section through said pipe, wherein the combined aperture exit areaA_(e) of the apertures is a function of widths D_(i) and D_(o), namelyA_(e) is no greater than A_(i)×D_(i)/D_(o)

Where only a single aperture is used, it has been found that Ae must notbe any greater than Ai×Di/2Do.

While the above interrelation, namely for a plurality of apertures whereAe≦Ai×Di/Do and for a single aperture Ae≦Ti×Di/2Do, means it is possibleto utilize apertures whose total combined cross-sectional area Ae isless than Ai×Di/Do or Ai×Di/2Do, typically, due to the desire to utilizean apparatus which utilizes the largest flow rate possible, it isusually greatly preferred that the greatest possible aperture exit areabe used. Accordingly, more than one aperture will typically be desiredto be used (thus the aperture exit area Ae may be twice as large than ifonly one aperture were used), and further that the aperture exit area Aeequal Ai×Di/Do, as such will give the greatest “throughput” of liquidwhich can be provided with gas microbubbles over a given time.

Accordingly, in a highly preferred embodiment, the pipe means willpossess more than one aperture, and the exit area of each of theapertures will be equal to Ai×Di/Do.

In order for the above formula of Ae≦Di×Di/Do apply for pipe membershaving more than one aperture, it is necessary that the pipe member benot only symmetric in cross-section, but further it have substantiallyidentical moments of inertia about two axis in a plane of cross-sectionthrough said pipe. This encompasses pipes having circular, square,hexagonal, octagonal and the like having uniform cross-sectional shape,but not to pipes having, for example, a rectangular cross-section. Asmore fully explained in this disclosure, for geometric cross-sectionalareas which although symmetric but which do not have identical momentsof inertia about at least two axis of a plane of cross-section, such asfor rectangular pipe, such formula does not hold true, and otherinter-relations may apply. However, in the case of rectangular pipe ofuniform thickness, as is more fully explained below, it has beendiscovered that the required interrelation between exit areas of theapertures Ae, the dimensions of the pipe, and the cross-sectional areaAi of the pipe for microbubbles of the desired size to be produced bedefined asAe≦A _(i) ×[D ₃ +D ₄ ]/[D ₁ +D ₂]where D₁ is the major exterior side length, D₂ is the minor exteriorside length, D₃ is the major interior side length, and D₄ is the minorinterior side length. However, as rectangular pipe is difficult toacquire, the more common application of this invention will be to pipemembers having circular or square profiles which have identical momentsof inertia about two or more axis in the plane of cross-section.

Accordingly, in a highly preferred embodiment, the pipe means of thepresent invention is of uniform wall thickness and has a maximuminterior width D_(i) and a maximum exterior width D_(o), further havingidentical moments of inertia about at least two separate orthogonal axisin a cross-sectional plane through said pipe means; said apertureshaving a combined cross-sectional exit area A_(e) defined as a functionof widths D_(i) and D_(o) and said cross-sectional area A_(i) of saidpipe means, wherein AC is substantially equal to A_(i)×D_(i)/D_(o)

It is highly preferred, although not absolutely necessary, that there bea vertical surface which created jets of gas/liquid mixture which exitfrom such apertures may impact against, in order to assist in thecreation of microbubbles of gas within the liquid.

Accordingly, in a further refinement of the apparatus of the presentinvention, such apparatus further consists of substantially verticalsurface means adapted to be impacted by said liquid when said liquid isdirected horizontally outwardly from said pipe means by each of saidapertures.

It is further preferred, although not absolutely necessary, that thecollection vessel for containing the resultant liquid havingmicrobubbles contained therein form part of an integral structure withthe pipe means and together form a single containment vessel in whichthe pipe means is located. While there are a number of advantages tousing an integral containment vessel having the pipe member therewithinas explained later within this specification, including the ability tocreate microbubbles within the gas/liquid mixture under an ambientgaseous pressure within such containment vessel, one particularadvantage is that, if desired, and if the gas/liquid mixture in the pipemeans is expelled from the apertures under sufficient pressure, thesides of the containment vessel may be used as the vertical surfaceagainst which the horizontal streams of gas/liquid which exit theapertures may be directed.

Accordingly, in a further broad embodiment of the present invention, theapparatus of the present invention comprises a vessel adapted to bepositioned substantially vertically and adapted to contain a volume ofgas in an upper portion thereof; means for introducing gas bubbles, themajority of which are of a size greater than 100 microns, into a liquidto form a liquid-gas mixture; elongate, hollow pipe means within saidvessel of interior cross-sectional area A_(i), for conveying said liquidwhen in a pressurized state to an interior of said vessel, substantiallysymmetrical in cross-section, situate centrally in said vessel andproximate said upper portion of said vessel and extending substantiallyvertically downwardly within said vessel from said upper portionthereof, and having plug means situate at a lowermost distal end thereoffor preventing egress of liquid vertically downward from said distalend; and at least two apertures situate on said pipe means and disposedin one or more planes each substantially perpendicular to a longitudinalaxis of said pipe means, extending from an interior of said pipe meansto an exterior of said pipe means, each adapted to direct said liquidunder pressure substantially horizontally outwardly from said pipemeans.

Again, in a preferred embodiment, where symmetrical pipe means such as acylindrical, square, hexagonal, octagonal, or even a triangular (equalsided) pipe member is used, the apparatus of the present inventioncomprises:

-   -   i) a containment vessel adapted to be positioned substantially        vertically and adapted to contain a volume of gas in an upper        portion thereof;    -   ii) elongate, hollow pipe means for providing said liquid to an        interior of said vessel, having a longitudinal axis and        substantially symmetrical in cross-section so as to have        identical moments of inertia about at least two separate axis in        a cross-sectional plane through said pipe means, of uniform wall        thickness, and having a maximum interior width D_(i) and a        maximum exterior width D_(o) and an interior cross-sectional        area A_(i), said pipe means situate substantially centrally in        said vessel and proximate said upper portion of said vessel and        extending substantially vertically downwardly within said        vessel, adapted for supplying a pressurized liquid to an        interior of said vessel, and having plug means situate at a        distal end thereof for preventing egress of liquid vertically        downward from said distal end;    -   iii) at least two apertures situate in said pipe means and        disposed in one or more planes each substantially perpendicular        to a longitudinal axis of said pipe means, each extending from        an interior of said pipe means to an exterior of said pipe        means, each adapted to direct said liquid substantially        horizontally outwardly from said pipe means, of combined        cross-sectional exit area A_(e), and    -   iv) said combined aperture exit area A_(e) of said apertures,        defined as a function of widths D_(i) and D_(o) and said        cross-sectional area A_(i) of said pipe means, wherein A_(e) is        no greater than, and preferably equal to, A_(i)×D_(i)/D_(o)

The aperture(s) may be of any geometric shape in cross section, such ascircular (ie cylindrical apertures), provided the exit area of suchaperture(s) in such pipe member meets the requirement for exit area Aeas discussed above in order to create microbubbles of a size in therange of 50 to 100 microns, and preferably 5-50 microns. In particular,the apertures may be one or more narrow horizontally-extendingrectangular slots, or alternatively one or more vertical slots in suchpipe member, all of which are easy to manufacture, either by drilling inthe case of cylindrical apertures, or cutting/milling in the case ofvertical or horizontal slots.

Importantly, it has further been discovered that apertures in the pipemember of a maximum dimension in excess of a certain amount may not formmicrobubbles of the required small size (5-50 microns).

In particular, the maximum gap “G”, namely the maximum cross-sectionaldimension that the aperture may possess is a function of the innercross-sectional area of the pipe member divided by the outercircumference of the pipe member.

Accordingly, in such cases, where the aperture(s) are of a horizontallyextending rectangular slot, of vertical depth G, where the pipe memberhas an exterior circumference C, G should preferably be no greater thanAi/C in order to form microbubbles when said liquid-gas mixture isexpelled from the pipe member via such aperture(s).

Likewise, where the aperture(s) are of a circular cross-section (iecylindrical), the diameter of such aperture should preferably be nogreater than Ai/C.

Again, it is possible to utilize apertures of maximum dimension (ordiameter, as the case may be) less than Ai/C, and still create gasmicrobubbles of the desired size of 5-100 microns. Accordingly, a largenumber of small apertures, where the total combined aperture area Aeadds up to the maximum aperture area [Ai×Di/Do] may be used, in order tointroduce microbubbles in as great a quantity of liquid over a giventime. However, having to drill large numbers of small apertures adds tothe cost and time in the manufacture of the pipe member and thus of theapparatus of the present invention. It is much less expensive and lesstime-consuming to drill/mill as few a number of apertures as possible(see discussion below as to what the minimum number of apertures may befor a circular pipe).

The above relationship for the aperture exit area A_(e) is derived fromthe surprising observation that the maximum aperture dimension (i.e. the“gap”) through which the gas/liquid mixture must pass is determined fromthe experimentally-derived observation that the aperture dimension,hereinafter referred to as the “gap”, which best creates microbubbles ofthe desired small size, is determined by the relationship gap“G”=A_(i)/(pipe outer circumference).

For example, for a circular conduit/pipe of minor diameter D_(i), outerdiameter D_(o), and cross-sectional area Ai=πD_(i) ²/4 it has been foundthat for a rectangular aperture cut perpendicularly into the side of thepipe, to a depth of ½ the pipe diameter, so as to create an aperture toallow egress of a gas/liquid mixture under pressure therethrough, themaximum permissible “gap” G, namely the maximum vertical height of suchhorizontal slot, is:A _(i)/(pipe outer circumference)=πD _(i) ²/(4_(—) πD _(o))=D _(i) ²/4D₀  (Eq'n. #1)

The surface exit area Ae of two slots each formed over ½ the innerdiameter of the pipe D_(i) is calculated as follows:A _(e)=2×gap×½π×D _(i)Thus the maximum exit area A_(e) of such apertures for a circular pipemember is thus equal toAe=2×D _(i) ²/4D _(o)×½π×D _(i) =πD _(i) ³/4D _(o).  (Eq'n. # 2)

Accordingly, Ae stated more generally in terms of A_(i), where Ai=πD_(i)²/4 may be stated as follows:$A_{c} = {\frac{\pi\quad{Di}^{3}}{4{Do}} = {{\begin{matrix}{\pi\quad{Di}^{2}} \\4\end{matrix} \times {D_{i}/D_{o}}} = {{Ai} \times {{Di}/{Do}}}}}$

Where only one exit aperture is utilized, maximum exit area is=πD_(i)³/8D_(o), and stated in terms of Ai is equal to:Ai×Di/(2Do)

In view of the above, the minimum number of apertures in a circular pipemay be determined. In this regard, in a preferred embodiment of theapparatus of the present invention, for the reasons discussed above,namely the desire to use the greatest amount of “throughput” for theapparatus with the least number of holes/apertures, and thus introducemicrobubbles into the greatest volume of liquid in the shortest time,the largest-sized aperture utilizable equals Ai/C. In order to achieveas much throughput of liquid which has microbubbles introduced therein,the apparatus in a preferred embodiment will not only possess aperturesof maximum size, but also the combined exit area Ae of such apertureswill equal the maximum permissible area in order that the apparatus beable to process (ie introduce gas microbubbles) into as much liquid aspossible for a given time.

Accordingly, in the case of cylindrical pipe, having circular(cylindrical) apertures, the minimum number of holes(apertures) whichcan be used is determined by reference to Eq'n. #2, which defines themaximum exit area for a circular pipe member, namely:Ae=πD _(i) ³/4D _(o)

Although the surface exit area of a circular hole in a cylindrical pipeforms a “saddle-like” exit area on the surface of the pipe, for smalldiameter apertures relative to the diameter of the pipe, the combinedsurface exit area of all apertures is approximately equal to the numberof apertures multiplied by the exit area A_(aperture) of each aperture:Ae(max)=n×A _(aperture(max)) =n×(π×Da ²/4)As discussed, Da is preferably no greater than Ai/C. Accordingly,substituting Ai/C for Da produces the following: $\begin{matrix}{\begin{matrix}{{{Ae}\quad\left( \max \right)} = {n \times \left( {\pi \times {\left\lbrack {\left( {\pi \times {{Di}^{2}/4}} \right)/\left( {\pi \times {Do}} \right)} \right\rbrack^{2}/4}} \right.}} \\{= {\pi\quad{D_{i}^{3}/4}D_{o}}}\end{matrix}{n = \frac{16{Do}}{Di}}} & \left( {{Eq}^{\prime}{n.\quad 6}} \right)\end{matrix}$The above equation for Ae(max) can be equated to Eq'n. # 2 for theAe(max) of a circular pipe, and solved for “n” as follows:$\begin{matrix}{{{Ae}\quad\left( \max \right)} = {n \times \left( {\pi \times {{Da}^{2}/4}} \right)}} \\{= {n \times \left( {\pi \times {\left\lbrack {{Ai}/C} \right\rbrack^{2}/4}} \right)}} \\{= {n \times \left( {\pi \times {\left\lbrack {\left( {\pi \times {{Di}^{2}/4}} \right)/\left( {\pi \times {Do}} \right)} \right\rbrack^{2}/4}} \right.}}\end{matrix}$Accordingly, since Eqn. 6 may, depending on the ratio of Do/Di, producea fractional value for the number of holes “n”, in a preferredembodiment, the minimum number of circular apertures in a circular pipemember for maximum flow of liquid is defined by the followingexpression, namely:n=nearest whole integer to [16×D _(o) /D _(i)]  (Eq'n. 6A).It is noted that since the maximum combined aperture exit area Ae forcylindrical pipe is Ai×Di/Do, for apertures of small diameter D_(A)relative to the diameter of the cylindrical pipe, the following is true:Ae _(max) =n×πD _(A(Max)) ²/4and thusAi×Di/Do=n×πD _(A(Max)) ²/4The above allows us to solve for the maximum diameter of the aperturesD_(A(max)), where for circular pipe, ${Ai} = \frac{\pi\quad{Di}^{2}}{4}$follows:π×Di²/4×Di/Do==n×π×D _(A(Max)) ²/4

thus$D_{A\quad{({MAX})}} = \sqrt{{Di}^{3}/\left\lbrack {n \times {Do}} \right\rbrack}$

stated alternatively,$D_{A\quad{({MAX})}} = {\sqrt{4} \times {Ai} \times {{Di}/\left\lbrack {n \times \pi \times {Do}} \right\rbrack}}$

It is usually the case for most cylindrical pipe having diameters Di andDo that “n” must be greater than 2 for most pipe, namely there mustusually be a plurality of apertures, since otherwise the calculateddiameter D_(A) results in a diameter greater than both the interiordiameter Di and the exterior diameter Do, which is a physicalimpossibility, as diameter D_(A) can only be as large as, or smallerthan, Di and Do.

The above value D_(A(MAX)) for a circular pipe having cylindricalapertures may, in instances where there are relatively few number ofapertures (ie n is a low number, but greater than one as per the above)give values of D_(A) which are higher than Ai/(outer circumference ofpipe) and which are too high and which will generally not producemicrobubbles of desired size (ie less than 50 microns). Accordingly, thetwo criteria which are preferably satisfied in order to formmicrobubbles of the desired size are that Ae(max)=Ai×Di/Do, andD_(A(MAX))≦Ai/(Circumference of Pipe).

For a square conduit of inner dimension D_(i) and outer dimension D_(o),having inner flow area A_(i)=D_(i) ² and outer circumference 4 Do, for ahorizontally extending slot of Gap “G”, it has been found that themaximum gap is likewise the flow area through the pipe Ai divided by theexterior circumference of the (square) pipe, being 4Do. Accordingly, themaximum vertical slot depth “G” for a square pipe may be stated asfollows:${{{Gap}{''}}{G{''}}\quad({Max})} = {\frac{A_{i}}{circumference} = \frac{D_{i}^{2}}{4D_{o}}}$

The exit area A_(e) for a plurality apertures in a square pipe may thusbe calculated, knowing such maximum Gap “G”. Accordingly, where theapertures comprise a pair of rectangular slots of vertical depth equalto the above Gap (Max), the exit area Ae for the apertures may becalculated as:A _(e)=2×Gap(max)×(½D _(i) +D _(i)+½D _(i))

Accordingly, expressed in terms of inlet area Ai for the square pipe, Aemay be stated as follows:$A_{c} = {{2 \times \frac{D_{i}^{2}}{4D_{o}} \times \left( {2D_{i}} \right)} = {\frac{4{Di}^{3}}{4D_{o}} = {{{Di}^{2} \times \frac{D_{i}}{D_{o}}} = {{Ai} \times {{Di}/{Do}}}}}}$

Again, where there is only one aperture in such square pipe, Ae is thus:A _(e)=Gap(max)×(½D _(i) +D _(i)+½D _(i))and thus, expressed in terms of Ai, is thus:Ae=Ai×Di/(2×Do)

As in the case of circular apertures in circular pipe, where there arecircular apertures in square pipe, the diameter D_(A(MAX)) may be solvedfor as follows:Ae=Ai×Di/Do  (1)Ae=n×π×D _(a) ²/4  (2) where ‘n’ is the number of aperturesEquating (1) with (2) allows for the diameter D_(A(MAX)) to be solvedfor as follows: $\begin{matrix}{{{Ai} \times {{Di}/{Do}}} = {n \times \pi \times {D_{a}^{2}/4}}} \\{D_{A\quad{({MAX})}} = {\sqrt{4 \times {{Di}^{3}/\left\lbrack {n \times \pi \times {Do}} \right\rbrack}} =}} \\{= \sqrt{4 \times {Ai} \times {{Di}/\left\lbrack {n \times \pi \times {Do}} \right\rbrack}}}\end{matrix}$

Again, it is usually the case for most square pipe having interior widthDi and exterior width Do that “n” must be greater than 2 for most pipe,namely there must usually be a plurality of apertures, since otherwisethe calculated diameter D_(A) of the cylindrical aperture results in adiameter greater than either the interior width Di or the exterior widthDo, which is a physical impossibility, as diameter D_(A) can only be aslarge as, or smaller than, Di and Do.

Again, the above value D_(A(MAX)) for a square pipe having cylindricalapertures may, in instances where there are relatively few number ofapertures (ie n is a low number, but as per the above, greater than one)give values of D_(A) which are higher than Ai/(outer circumference ofpipe) and which are too high and which will generally not producemicrobubbles of desired size (ie less than 50 microns). Accordingly, thetwo criteria which are preferably satisfied in order to formmicrobubbles of the desired size are that Ae(max)=Ai×Di/Do, andD_(A(MAX))=Ai/(Circumference of Pipe).

It has been discovered that the above relationship(s) hold true for anypipe of symmetrical cross-sectional area and having at identical momentsof inertia about at least two axis in a plane of cross-section throughsuch pipe.

For example, for a triangular pipe member (of equal interior side lengthDi and equal exterior side length Do so as to be symmetrical and haveidentical moments of inertia about at least two axis in a plane ofcross-section through such pipe member), the interior cross-sectionalarea Ai of such pipe member of interior side length Di is:${Ai} = {\frac{\sqrt{3}}{4}{Di}^{2}}$

For two identical horizontal slots (apertures) cut into such pipe toform a “gap” of vertical height “G”, where such slots to a depth so asto provide access to one-half of the interior area Ai of such pipemember, the maximum gap (ie vertical depth of each slot) is againdetermined by the relationship${{Gap}\quad({Max})} = {{{{Ai}/{pipe}}\quad{outer}\quad{circumference}} = {{{{Ai}/3}{Do}}==\frac{\sqrt{3}{Di}^{2}}{12{Do}}}}$

The exit area of such two apertures is accordingly determined as theproduct of the gap multiplied by the perimeter of the gap. Accordingly,$\begin{matrix}{{{Ae}\quad\left( \max \right)} = {2 \times {gap} \times \left( {{Di} + {{1/2}{Di}}} \right)}} \\{= {2 \times \frac{\sqrt{3}}{12{Do}}{Di}^{2} \times \frac{3}{2}{Di}}} \\{= {\frac{\sqrt{3}}{4}\frac{{Di}^{3}}{Do}}}\end{matrix}$Expressed in terms of Ai,${{Ae}\quad\left( \max \right)} = {{\frac{\sqrt{3}}{4}{Di}^{2} \times \frac{Di}{Do}} = {{Ai} \times \frac{Di}{Do}}}$

The present invention, in a further of its broad aspects, relates to amethod for creating microbubbles of gas in a liquid and exposing them tomatter entrained in said liquid. Accordingly, in one broad aspect of themethod of the present invention, such method comprises the steps of:

providing gas to said liquid to form a gas/liquid mixture;

directing said gas-liquid mixture into a hollow pipe member, said pipemember having a maximum interior width D_(i) and a maximum exteriorwidth D_(o), said pipe member situate proximate an upper portion of acontainment vessel and extending into an interior of said containmentvessel, said upper portion of said containment vessel containing saidgas being under pressure, and a bottom portion of said containmentvessel substantially containing said liquid;

injecting said gas-liquid mixture under pressure via said pipe member,into said containment vessel;

spraying substantially radially outwardly from said pipe member saidgas-liquid mixture into said upper portion of said containment vesselvia at least two apertures in said pipe member;

said at least two apertures in said pipe member in communication withsaid gas-liquid mixture in said pipe member and having a combined areaA_(e) sized as a function of a maximum interior widths D_(i) and maximumoutside width D_(o) and a cross-sectional area A_(i) of said pipemember, wherein A_(e) is substantially equal to:A_(i)×D_(i)/D_(o)

and

removing from said bottom portion of said containment vessel said liquidwhich has been exposed to said microbubbles.

In yet another aspect of the method of the present invention, suchmethod comprises a method for converting a liquid-gas mixture havingbubbles of gas therein the majority of which are greater than 5-100microns in size to a liquid-gas mixture having microbubbles of gastherein the majority of which are of a size between 5-100, comprisingthe steps of:

directing said gas-liquid mixture having bubbles of gas therein themajority of which are greater than 5-100 microns in size into a hollow,substantially vertical pipe member, having a maximum interior widthD_(i) and a maximum exterior width D_(o);

spraying said gas-liquid mixture substantially radially outwardly fromsaid pipe member via a plurality of apertures in said pipe member, sothat said gas-liquid mixture contacts a vertically extending surface;

said plurality of apertures in said pipe member in communication withsaid gas-liquid mixture in said pipe member and having a combined areaA_(e), said apertures sized as a function of said maximum interior widthD_(i) and said maximum outside width D_(o) and a cross-sectional areaA_(i) of said pipe member, wherein A_(e) is no greater than, andpreferably equal to:A _(i)×D_(i)/D_(o)

collecting a resulting gas-liquid mixture having microbubbles of gasentrained therein in a vessel; and

removing said gas-liquid mixture from said vessel.

In a further refinement of the methods of the present invention, onesuch method further comprises the step of collecting within said bottomportion of said vessel said liquid with microbubbles entrained thereinand withdrawing said liquid from said bottom of said vessel at a rateapproximately equal to a rate at which said liquid is introduced intosaid containment vessel.

In yet a further refinement of the aforesaid methods, the rate ofwithdrawing the liquid from the bottom of the vessel is substantially ata rate which microbubbles entrained in said liquid rise in the vessel,so that at a time when liquid is removed from said bottom of said vesselsaid microbubbles will have travelled upwardly a distance through saidliquid equal to a depth of liquid in the bottom of the vessel.

In yet a further aspect of the method of the present invention, theliquid-gas mixture sprayed from said pipe member may be passed through abaffle plate member positioned in the containment vessel below said pipemember and intermediate said upper portion and said bottom portion ofsaid containment vessel, and the rate of injection and removal ofgas-liquid from the vessel adjusted so that baffle plate member ispositioned above the level of the liquid in the vessel.

In order for the apparatus and method of the present invention to formmicrobubbles, the pressure of the gas in the upper portion of the vessel(back pressure) need be of a pressure of at least 10 psig to 15 psig,and preferably at least 20 psig to 30 psig. The initial-gas liquidmixture, in order to be provided to the apertures and sprayed therefrom,must necessarily, due to a small pressure drop across the apertures, besupplied at a slightly higher pressure than the pressure of the gaswithin the upper portion of the vessel (i.e. back pressure), in order tobe effectively sprayed into the interior of the vessel. The step ofspraying the liquid-gas mixture substantially radially outwardly via theapertures may further in a preferred embodiment be adapted to spray suchliquid-gas mixture against the sides of the containment vessel.

From another perspective, the invention in a preferred embodimentcomprises a method for continuously purifying a liquid containingimpurities by exposing the liquid and impurities for a time in asubstantially vertically containment vessel to microbubbles in the rangeof 5-100 microns in diameter, comprising the steps of:

directing a gas-liquid mixture containing impurities and bubbles of gasthe majority of which are in excess of 100 microns in diameter into ahollow pipe member, said pipe member of uniform thickness and having amaximum interior width Di and a maximum exterior width Do and identicalmoments of inertia on two axis in a plane of cross-section through saidpipe means, said pipe means situate proximate an upper portion of saidcontainment vessel and extending vertically downwardly in an interior ofsaid containment vessel, said upper portion of said containment vesselcontaining said gas, and being under pressure of at least 10 psig andpreferably 15 psig or higher;

injecting said gas-liquid mixture, under a pressure of at least 5 psighigher than said gas in said containment vessel, into said vessel viasaid pipe member;

spraying said gas-liquid mixture substantially horizontally outwardlyfrom said pipe member into said upper portion of said containment vesselvia a plurality of apertures in said pipe member so that said gas-liquidmixture contacts interior sides of said vessel;

said plurality of apertures in said pipe member in communication withsaid gas-liquid mixture in said pipe member and having a combined areaA_(e), said apertures sized as a function of said maximum interior widthD_(i) and said maximum outside width D_(o) and a cross-sectional areaA_(i) of said pipe member, wherein A_(e) is no greater than:A _(i)×D_(i)/D_(o)collecting said gas-liquid mixture, now having microbubbles of gasentrained therein the majority of which are now of a size less than 100microns in diameter, in a bottom portion of said containment vessel;

removing, from said bottom portion of said vessel, said liquid with gasmicrobubbles entrained therein at a rate which said microbubblesentrained in said liquid rise in said vessel so as to permit said gasmicrobubbles time to react with impurities in said liquid; and

supplying said liquid-gas mixture to said pipe member substantially at arate at which said liquid-gas mixture having gas microbubbles entrainedtherein is removed from the bottom of said vessel.

Advantageously, the present invention in a particular refinement of bothof one of the method and apparatus of the present invention, makes useof a sorting phenomenon in order to obtain microbubbles of the desiredsize.

Specifically, in a particular embodiment where a gas-liquid mixturehaving gas bubbles of substantially large size (>100 microns) entrainedtherein is sprayed outwardly from a pipe member and captured in acontainment vessel, liquid having some large (>100 microns) as well assmall (<100 micron) gas bubbles (but preferably a preponderance of smallgas bubbles) is collected in said vessel. However, gas bubbles in saidliquid which fall vertically down in said vessel when expelled from saidaperture tend to fall to various depths in said containment vessel,before starting to rise in such vessel, depending on the size of the gasbubble entrained in surrounding liquid. Specifically, larger gas bubbleswithin the liquid tend to fall a lesser distance downwardly in liquidcollecting at a bottom portion of the containment/collection vessel thansmaller gas bubbles.

Accordingly, by proper vertical positioning of a liquid-withdrawal tubefrom the containment vessel this “sorting” of bubbles within the liquidcollecting in the bottom portion of the vessel can be taken into accountin obtaining liquid having gas bubbles of the lesser (more desirable)smaller diameter Specifically, positioning of such withdrawal tube onsuch vessel at a position somewhat above a lowermost portion of saidvessel and immediately below a lowermost level in said vessel whichbubbles of a size larger than 100 microns initially fall to beforerising in said vessel, and at a level within said bottom portion of saidvessel which bubbles of a size less than 100 microns initially fall tobefore rising in said vessel, will allow the withdrawal tube to withdrawfrom said vessel only a gas-liquid mixture having smaller (ie<100micron) bubbles.

Accordingly, in a preferred method of the present invention takingadvantage of the above “sorting” principle in order to obtain gasmicrobubbles of a size less than 100 microns, such method comprises amethod for producing a liquid having gas microbubbles therein themajority of which are of a size less than 100 microns, comprising thesteps of:

providing gas to said liquid to form a gas/liquid mixture;

directing said gas-liquid mixture into a hollow pipe member, said pipemember having a maximum interior width D_(i) and a maximum exteriorwidth D_(o), said pipe member situate proximate an upper portion of acontainment vessel and extending into an interior of said containmentvessel, said upper portion of said containment vessel containing saidgas being under pressure, and a bottom portion of said containmentvessel substantially containing said liquid;

spraying substantially radially outwardly from said pipe member saidgas-liquid mixture into said upper portion of said containment vesselvia at least two apertures in said pipe member; and

removing from said bottom portion of said containment vessel, at aposition somewhat above a lowermost portion of said vessel, saidgas-liquid mixture;

said position being a position immediately below a lowermost level insaid vessel which bubbles of a size larger than 100 microns initiallyfall to before rising in said vessel, and at a level within said bottomportion of said vessel which bubbles of a size less than 100 micronsinitially fall to before rising in said vessel.

In a further embodiment the invention consists of an apparatus formaking use of the “sorting” phenomenon.

Accordingly, in such refinement of the apparatus of the presentinvention, the containment vessel of the present invention comprisesgas-liquid withdrawal means, such withdrawal means in communication withan interior of the vessel proximate a bottom portion thereof, vessel,adapted to withdraw a gas-liquid mixture having microbubbles ofentrained gas therein from said interior of such vessel, such withdrawalmeans situate on said vessel at a position, said position being at alevel on said vessel below a lowermost level within said vessel whichbubbles of a size larger than 100 microns fall to before rising inliquid in said vessel, and at a level which bubbles of a size less than100 microns fall to before rising in said vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings, showing selected embodiments of the invention,are non-limiting and illustrative only. For a complete definition of thescope of the invention, reference is to be had to the summary of theinvention and the claims.

FIG. 1 shows a front view of one embodiment of the apparatus of thepresent invention for creating microbubbles of gas, said apparatus inthe embodiment shown using a cylindrical pipe member and a plurality ofhorizontally-extending cylindrical apertures;

FIG. 2 is an enlarged view of area “A” of FIG. 1;

FIG. 3 is an enlarged perspective view of items 24 and 25, area “B” ofFIG. 2, showing in a particular embodiment of the invention wherein item24 (pipe member) is cylindrical having circular apertures 32 therein;

FIG. 4 is a view of an alternative embodiment of the present invention,similar to that shown in FIG. 1, showing utilization of an inclined butsubstantially vertical baffle member;

FIG. 5 is an enlarged view of a particular embodiment showing of a pipemember of the present invention of circular cross-section, furthershowing an embodiment of the pipe member having horizontally-extendingrectangular slots formed in such pipe member for acting as apertures topermit the expulsion of a gas-liquid mixture from such pipe member;

FIG. 5A is a section through the pipe member of FIG. 5, taken alongplane X-X;

FIG. 5B is a section through the pipe member of FIG. 5, taken alongplane Y-Y;

FIG. 6 is an enlarged view of a particular embodiment showing of a pipemember of the present invention of square cross-section, further showingan embodiment of the pipe member having horizontally-extendingrectangular slots formed in such pipe member for acting as apertures topermit the expulsion of a gas-liquid mixture from such pipe member;

FIG. 6A is a section through the pipe member of FIG. 6, taken alongplane X-X;

FIG. 7 is an enlarged view of a particular embodiment showing of a pipemember of the present invention of triangular (equal sided)cross-section, further showing an embodiment of the pipe member havinghorizontally-extending rectangular slots formed in such pipe member foracting as apertures to permit the expulsion of a gas-liquid mixture fromsuch pipe member;

FIG. 7A is a section through the pipe member of FIG. 7, taken alongplane X-X;

FIG. 8 is an enlarged view of a particular embodiment showing of a pipemember of the present invention of rectangular cross-section, furthershowing an embodiment of the pipe member having horizontally-extendingrectangular slots formed in such pipe member for acting as apertures topermit the expulsion of a gas-liquid mixture from such pipe member;

FIG. 8A is a section through the pipe member of FIG. 7, taken alongplane X-X 10

FIG. 9 is a side view similar to FIG. 1 showing another embodiment ofthe apparatus of the present invention, wherein the apertures forforming the microbubbles are situate in a plug member which is itselfsituated at the extreme lowermost distal end of the plug member; 1 FIG.10 is an enlarged view of area “A” of FIG. 9;

FIG. 11 is yet a further side view similar to FIGS. 1 and 9, showing yetanother embodiment of the apparatus of the present invention, in thiscase having circular apertures situate in the plug member at the extremelowermost end of the pipe member; 20

FIG. 12 is an enlarged view of area “A” of FIG. 11;

FIG. 13 is an enlarged view of the baffle plate member shown in FIGS. 1,9, and 11; FIG. 14 is a cross-sectional view of a particular embodimentof the apparatus of the present invention which was selected to conducttests on;

FIG. 15 is schematic view of additional test apparatus used to test theoperability of the apparatus and method of the present invention; 30

FIG. 16 is a table setting out test data obtained using the testapparatus of FIGS. 14 and 15; and

FIG. 17 is a graph showing a plot of aperture exit area Ae as a functionof bubble diameter, such data obtained from data using the testapparatus shown in FIGS. 14 and 15; and

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows one embodiment of the apparatus 10 of the present inventionfor producing microbubbles 12 in a liquid 14.

A means 16 for introducing gas bubbles 20 into such liquid 14 flowing inpipe 9 is provided. Means 16 may be a venturi, namely aconverging-diverging nozzle, as known in the art, having at theconverging portion an aperture 17 through which gas, typically althoughnot always air, is drawn and flows in the form of bubbles 20 into theliquid, to form a gas-liquid mixture 22. Alternatively, and moretypically, means 16 is simply an orifice to permit the injection of gasunder pressure into said liquid 14 in pipe member 12, resulting information of gas bubbles 20 within liquid 14, which is under a resultingpressure.

The supply of gas may be from ambient air, if air is the desired gas tobe introduced, as shown in FIG. 1, or alternatively may be from apressurized tank of gas (not shown), if some other form of gas (such asH₂ or CO₂) is desired to be introduced.

Gas bubbles 20 entrained in such gas-liquid mixture 22 in the abovemanner are typically of a size greater than 100 microns, or at least amajority of gas bubbles 20 entrained in such gas-liquid mixture 22 areof a size greater than 100 microns, at typical ambient temperature andpressure (22° C. and 1 atmosphere).

One of the purposes of the apparatus 10 of the present invention is toreduce the bubble size of the gas bubbles 20 within the gas-liquidmixture 22 to a size less than 100 microns, and preferably to a size inthe range of 5-50 microns, in order to increase the ability of the gasin the gas-liquid mixture 22 to react with materials or substancesentrained in the gas-liquid mixture 22, for the purposes of purifyingand/or causing certain entrained substances in such liquid 14 toprecipitate out of such gas-liquid mixture 22, thereby ridding suchliquid 14 of such substances.

The gas-liquid mixture 22, having gas bubbles 20 therein the majority ofwhich are of a size greater than 100 microns, is thereafter conveyedtypically by means of a hollow pipe or conduit 24 to an elongate, hollowpipe member 24, typically although not necessarily, situate within acontainment vessel 40, as shown in FIG. 1.

Pipe member 24 contains aperture means consisting of a one or moreapertures 32, extending from an interior 33 of such pipe member 24 to anexterior 37 of pipe member 24 (see enlarged view of one embodiment ofpipe member 24 shown in FIG. 3, wherein pipe member 24 is cylindrical incross-section, having a plurality of cylindrical apertures therein).Each of apertures 32 may be of any geometric shape, but preferably areof a cylindrical shape as shown in FIG. 3, a cylindrical aperture beingthe resultant shape that results from drilling of such aperture 32during manufacture using a circular drill bit, drilling being one of theeasiest means of forming such apertures 32. Each of said apertures 32extend horizontally outwardly and substantially perpendicular to alongitudinal axis of the pipe member 24. Pipe member 24 is positionedsubstantially vertically, as shown in FIG. 1, and is adapted to receivethe liquid-gas mixture 22 and supply same under pressure to apertures32. Each of apertures 32 extend horizontally outwardly from interior 33of pipe member 24 to exterior 37 of pipe member 24. Pipe member 24further possesses a plug member 25, situate at a lowermost distal endthereof for preventing egress of liquid-gas mixture 22 from said pipemember 24.

As hereinafter explained, the size (both width and cross-sectional area)of such apertures 32 is dependent in a preferred embodiment on certainformulae which are preferably maintained to allow formation ofmicrobubbles 12 of a desired size, namely less than 100 microns, andpreferably 5-50 microns, when the gas-liquid mixture 22 is expelledunder pressure from the pipe member 24 via apertures 32.

A containment vessel 40 is further provided In a preferred embodiment,containment vessel 40 is an elongate, vertically-extending column,configured so as to receive therewithin pipe member 24 in an upperportion 42 thereof. Specifically, in the embodiment shown in FIG. 1,containment vessel 40 is formed of a vertical conduit 46, havingthreaded flange members 43 affixed [in the preferred embodiment bywelding for conduits of weldable metallic material and where suchconduits are of a plastic material such as polyvinyl chloride (PVC), byan adhesive or a bonding agent such chloroform] at each of a bottom andtop end 44,45 respectively. Flanges 41,43 are adapted to receive platemembers 47,48 at each of said top and bottom ends 44,45 which may bebolted to flange members 43 respectively by means of bolts 57, with anintervening gasket 59, so as to form an enclosed vessel 40.

The purpose of vessel 40 is to receive and contain for a time liquid 14expelled from said apertures 32 at a given level “x” within said vessel40. The resulting microbubbles 12 produced in the gas-liquid mixture 22which fall from apertures 22 into vessel 40 may react in the bottomportion 48 of vessel 40 with substances within the liquid 14, so as tocause impurities to precipitate out. The remaining (purified) liquid 15may then be removed from vessel 40 via a lower liquid withdrawal pipe51.

Alternatively, or in addition, the vertical length 50 of the bottomportion 48 of vessel 40 may act as a stratification column and takeadvantage of a “sorting” with respect to gas bubbles. In this regard,any remaining gas bubbles 14 of a relatively large size (ie in excess of100 microns in size) which may still be entrained in said gas-liquidmixture 22 along with smaller gas bubbles after the expulsion of thegas-liquid mixture from apertures 32 will tend to fall into bottomportion 48 of vessel 40. However, larger gas bubbles tend to fall to orabove a level (namely above line “X” as shown in FIG. 1) beforebeginning to rise in the liquid column contained in the bottom portionof vessel 40. On the other hand, smaller sized gas bubbles tend to fallto a level “Z” or below such level “Z” before beginning to rise withinsuch liquid, as shown in FIG. 1.

Accordingly, by positioning withdrawal pipe 51 at a level below a level“Z” to which the majority of larger gas bubbles fall, only liquid 15substantially having gas bubbles of a size less than 100 microns may beobtained when withdrawn from withdrawal tube 51. Such liquid 14, havinga majority of gas bubbles therein of a size less than 100 microns, maythen be transported via withdrawal pipe 51 to a further containmentvessel 52 (not shown) where such gas microbubbles entrained in theliquid 14 may then react (or further react) with substances within suchliquid 15, such as iron bacteria or other undesirable substances, so asto render such substances harmless or cause them to precipitate out ofsolution, leaving a purified liquid 15.

Although it is not necessary that vessel 40 be an enclosed vessel, inthe preferred embodiment it is desirable that vessel 40 be an enclosedvessel, as shown in FIG. 1. This allows two advantages to be realized.

Firstly, to improve the formation of gas microbubbles upon theliquid-gas mixture 22 being expelled from aperture means within pipemember 24, the side walls 55 of an enclosed vessel 40 may be used, wherethe pressure in pipe member 24 is sufficiently high, as a verticalsurface against which resulting jets 56 of gas-liquid may impingeagainst prior to falling from upper portion 42 of vessel 40 to bottomportion 48 of vessel 40. A depiction of this preferred embodiment isshown in enlarged view in FIG. 2. The impaction of the jets 56 of gasliquid against side walls 55 tends to cause larger gas bubbles entrainedin liquid 14 to break into microbubbles, thus aiding the formation ofgas microbubbles.

Secondly, the utilization of an enclosed vessel 40 assists inmaintenance of gas microbubbles within liquid 14 in the bottom portion48 of vessel 40, as the vessel 40 may be maintained under a relativepressure. In this regard, in a preferred embodiment, the internalrelative pressure in the upper portion 42 of vessel 40 is in the rangeof 25 psig or above, with the pressure of the gas-liquid mixture 22 inpipe member 24 being in the range of 5 psig or higher than the internalrelative pressure within vessel 40, to permit the gas-liquid mixture 22within such pipe member 24 to be expelled into upper portion 42 ofvessel 40 via apertures 32. The maintenance of a pressure within vessel40 less than the supplied pressure within pipe member 24 assists information of gas bubbles in liquid 14. The maintenance of a pressurewithin such vessel 40 higher than ambient assists in maintaining bubblesof a small size within the bottom portion of the vessel 40, which isuseful if the sorting feature described above is not desired to be usedand instead the bottom portion of vessel 40 is used as a type ofcontainment vessel to allow reaction of the gas microbubbles withsubstances within liquid 14, as further explained below.

The embodiment of the apparatus and the method of the present inventionwhere the “sorting” of bubbles according to size is employed and thewithdrawal pipe 51 is situated at a level below level “Z” to withdrawonly those gas bubbles the majority of which have a size less than 100microns, is particularly suited to a continuous as opposed to a batchprocess. Specifically, because the liquid which is withdrawn fromwithdrawal pipe 51 is substantially comprised of microbubbles, liquid 14having such microbubbles entrained therein may be continuously withdrawnfrom vessel 40 for subsequent processing in a reaction vessel (notshown) elsewhere.

Where the bottom portion 48 of vessel 40 is itself used as a reactionvessel to allow the microbubbles therein to react with substances insuch liquid 14, either a “batch” or a “continuous” process may beemployed. Specifically, where a batch process is employed, sufficientgas-liquid mixture 22 is discharged through apertures 32 to allow theliquid-gas mixture 22 to rise in vessel 40 to a level “x” approximatelyone-half to two-thirds the height of vessel 40. A period of time isallowed to pass, namely the period of time which it takes formicrobubbles of a size less than 100 microns to rise from a level at orbelow level “Z” (see FIG. 3) to level “X”. Thereafter the liquid 15 maybe withdrawn from vessel 40 by withdrawal pipe 51 at a position on suchvessel anywhere intermediate level x and the base of the vessel 40, andpreferably at a level close to level “Z”.

Where a continuous process of treating liquid 14 in containment vessel40 is desired to be employed, liquid 14 in the liquid-gas mixture 22 issupplied to the vessel 40 via pipe member 24 at a rate approximatelyequal to a rate at which the liquid 15 is withdrawn from vessel 40 viawithdrawal pipe 51. In addition, the rate of withdrawal of liquid 15(and the rate of supply of liquid 14) is adjusted so that at a time whenliquid is removed from said bottom portion 48 of vessel 40 themicrobubbles will have travelled upwardly a distance through liquid 14substantially equal to a majority of the depth of liquid 14 in saidbottom portion of said vessel, namely from approximately level “z” toapproximately level “x”. In order to facilitate the removal of liquid 15which has been exposed to microbubbles for such period of time, avertical baffle plate member 60 may be employed as shown in FIG. 4 todirect the flow of liquid having microbubbles entrained therein as shownin FIG. 4. In such embodiment withdrawal tube 51 is preferably situateclose to, but below level “X”, and withdraws liquid 15 which has beenexposed to gas microbubbles for the time that it takes such microbubblesafter having fallen from level “x” to level “z” on a first side 70 ofsuch baffle member 60 to rise on the other side 71 of baffle member 60from level “Z” to level “X”.

In a further embodiment, the apparatus 10 of the present inventionfurther includes a horizontal baffle plate member 80 (ref. FIG. 1 andFIG. 4), positioned intermediate upper portion 42 and bottom portion 48of vessel 40, and above level “x” of liquid 14 in the vessel 40, so thatgas-liquid mixture sprayed from pipe member 24 is permitted to passthrough such baffle member 80 when falling to bottom portion 48 ofvessel 40. Baffle plate member 80 is provided with a series of orifices82 (see FIG. 13 showing enlarged view of horizontal baffle member 80) topermit gas-liquid mixture 22 to further fall to bottom portion 48 ofvessel 40. Baffle plate member 80 further assists in converting gasbubbles 20 in gas-liquid mixture 22 to microbubbles.

Pipe member 24 having one or more apertures 32 therein may be any hollowelongate tubular member, substantially symmetrical in cross-section.FIGS. 5, 6, 7, and 8 show four separate embodiments, where such pipemember 24 is alternatively of, but not limited to, having a circular,square, triangular, and rectangular cross-sectional area respectively

In order for the apertures to best form microbubbles, in a preferredembodiment a specific mathematical relationship exists between theinterior area of the pipe member 24, and the combined exit area Ae ofapertures 32, where such pipe member 24 has a maximum exterior width Doand maximum interior width Di. Such relationship between the combinedexit area Ae of the apertures 32 and the inlet area Ai of the pipemember 24 is essentially a function of the thickness of the pipe member(namely the ratio of Di to Do), and is a definite relationship forsymmetrical pipe members 24 of uniform wall thickness.

Specifically, it has been found experimentally (see examples 1 and 2,below) and confirmed by derivation (see summary of invention, above)that for pipe members 24 of uniform wall thickness and having a maximuminterior width Di and a maximum exterior width Do, where the pipe member24 has identical moments of inertia about at least two separate axis ina plane of cross-section through such pipe member 24, that for formationof microbubbles of gas in a liquid 14 (ie bubbles of less than 100microns) under conditions of standard temperature and pressure, Ae canbe less than or equal to, but no greater than Ai×Di/Do where there exista plurality of apertures 32 in pipe member 24. Where only one aperture32 exists in pipe member 24, such aperture may only have across-sectional area no greater than Ai×Di/2Do.

FIG. 5 shows a detail view of a pipe member 24 of the present invention,having a circular cross-section, of maximum internal width Di, andmaximum exterior width Do, and internal area Ai=π×Di²/4, FIG. 5 alsoshows the configuration of pipe member 24 and apertures 32 used todetermine the relationship between inlet area Ai and combined apertureexit area Ae. Two rectangular slots 90 were formed in pipe member 24, onopposite sides thereof, each to a depth of ½ Do. Each rectangular slot90 forms an exit area equal to “gap”×π×Di (see FIG. 5B), so as, in thecase of two rectangular slots 90, to form a combined exit areaAe=2×“gap”×π×Di.

It was experimentally found (see example 1, below) that the maximumcombined exit area for at least two or more apertures was Ae can be nogreater than Ai×Di/Do where bubbles of a size less than 100 microns aredesired.

Having a maximum combined exit area Ae means that the aperture “gap”shown in FIG. 5 will be a maximum Accordingly, where maximum throughputof gas-liquid mixture 22 is required through apparatus 10 of the presentinvention, the maximum combined aperture exit area Ae is used. WhereAe=Ai×Di/Do, setting this equal to 2×gap×π×Di and solving for the gap,this means the “gap” can only be [Ai×Di/Do]/2×π×Di which stated moresimply is equal to Ai/π×Do., where π×Do is the outer circumference ofpipe member 24.

Accordingly, in a further embodiment, a further restriction exist on thewidth of the “gap” shown in FIG. 5, namely that the “gap” be no greaterthan the quotient of Ai and the outer circumference of pipe member 24,namely π×Do. Stated in other terms, to form bubbles in the extruded jets56 of gas-liquid mixture 22 which is expelled from rectangular slots 90comprising apertures 32, such apertures 32 may only be of a maximumvertical depth (“gap”) of Ai/C, namely [π×Di²/4]/[π×Do] (ie Di²/4Do).Thus where the maximum aperture distance (ie the maximum “gap”) of Di²/4Do is used, so as to be required to drill the fewest slots or apertures32, the maximum “gap” of aperture is typically used, namelyAi/circumference of pipe member 24, which for a cylindrical pipe member24 is simply Di²/4 Do.

As may be seen from FIG. 5, pipe member 24 possesses uniform wallthickness (ie Do less Di is always a constant). Moreover, as may be seenfrom FIG. 5A, such pipe member 24 possesses at least two identicalmoments of inertia in a plane of cross-section, namely the moments ofinertia about axis I₁ and I₂ are identical, namely π/64 [Do⁴−Di⁴]

The same relationship applies in the case of pipe member 24 of squarecross-sectional area Ai, as shown in FIGS. 6 and 6A, of uniformthickness “t”. Thus for two rectangular slots 90 within square pipemember 24, as may be seen from FIG. 6A, the combined aperture exit areaAe may be calculated as 2×“gap”×[½Di+Di+½Di]. Where the maximum “gap” isdetermined by the surprisingly-found relationship of Ai/(circumferenceof pipe), namely Ai/4 Do, then Ae thus becomes 2×Ai/4Do×[2Di]=Ai×Di/Do.Again, a square pipe member 24 has identical moments of inertia abouttwo identical axis I₁ and I₂ in a plane of cross-section, namelyI₁=I₂=[Do⁴−Di⁴]/12

The same relationship applies in the case of pipe member 24 oftriangular (equal sided) cross-sectional area Ai, as may be seen fromFIGS. 7 and 7A. Thus for two rectangular slots 90 within equilateraltriangular pipe member 24 of depth equal to ½Do on one side as shown inFIG. 7A, as may be seen from FIG. 7A, the combined aperture exit areamay be calculated as 2×“gap”×[½Di+Di]. Where the maximum “gap” isdetermined by the surprising relationship of Ai/C, which in the case ofan equilateral triangle of interior maximum width Di equals Ai/3Do, thenAe=2×gap× 3/2Di=2×Ai/3Do× 3/2Di, which reduces again to Ae=Ai×Di/Do.Again, as may be seen from FIG. 7A, an equilateral sided triangular pipemember 24 has identical moments of inertia about two axis I₁ and I₂ in aplane of cross-section, namely I₁=I₂

For a symmetrical pipe member 24 which does not have identical momentsof inertia about two axis in a plane of cross-section, such as arectangular pipe member 24 as shown in FIGS. 8 and 8A (namely I₁≠I₂),the derived relationship of Ae=Ai×Di/Do does not apply.

However, in the case of a rectangular pipe member 24 having maximumexterior dimension D₁, minimum exterior dimension D₂, maximum interiordimension D₃, and minimum interior dimension D₄, as shown in FIGS. 8 and8A, the combined exit area Ae for two rectangular slots 90 as seen inFIG. 8A is determined as 2×“gap”×[½D₄+D₃+½D₄]. Again, using thesurprising result that the maximum “gap” equals Ai/C, namelyAi/[2×(D₂+D₁)], then Ae=2×gap×[D₄+D₃]=Ai×[D₄+D₃]/[D₂+D₁].

With respect to the location of the apertures 32 of the presentinvention, from which gas-liquid mixture 22 is expelled, apertures 32may be formed within pipe member 24, as shown in FIG. 1 and particularlyin enlarged view shown in FIG. 3 and FIGS. 4 through 8 inclusive.Alternatively, apertures 32 may be formed in plug member 25. FIG. 9, andFIG. 10 showing enlarged detail, illustrate formation of a pair ofrectangular slots 90 which serve as apertures 32 in plug means 25. FIG.11, and FIG. 12 showing enlarged detail, illustrate the employment of aplurality of cylindrical apertures 32 in plug member 25. Of course, asin the case where the apertures 32 are situate within the pipe member 24itself, such apertures may be of any geometrical cross-sectional area,with circular cross-sectional area being preferred due to the ease increating cylindrical apertures 32 having circular cross-sectional area,such as by drilling with circular drill bits.

EXAMPLE 1

A series of seventeen various-sized apparatus 10 were constructed inaccordance with one of the embodiments of the invention as contemplatedherein, namely that embodiment shown in FIG. 1, having a pair ofapertures 32 in the form of horizontally-extending rectangular slots 90,as shown in FIG. 5.

Each of the aforesaid seventeen test units comprised a shell (referredto above and below as a vessel 40), having in an upper portion 42thereof a downwardly extending, substantially vertical cylindrical pipemember 24 of various Di and Do, ranging from nominal pipe nominaldiameters of 0.50 inches to 10.0 inches.

Each of pipe members 24 for the various test units had a pair ofrectangular opposed slots 90 therein, as shown in FIG. 5. The exit areaAe for the pair of slots was set as the maximum, in accordance with therequirement Ae (max)=Ai×Di/Do. Because the width of each of the slots 90was the width Di of each pipe member 24 as shown in FIG. 5, the verticaldepth (ie “gap”) of each of the slots 90 was accordingly therebypre-determined due to the requirement that Ae=Ai×Di/Do, and wasgap_((max))=Ai/(outer circumference of pipe member 24).

Vessels 40 of various nominal diameter sizes were used and matched withcorresponding pipe members 24, with the vessel 40 having a nominaldiameter of approximately six times the pipe member 24 nominal diameter.This resulted in a matching of vessels 40 with pipe members 24, whereinthe vessel 40 nominal diameter ranged from a nominal 3.0 inch diameterto a 10.0 inch nominal diameter.

Various lengths of vessel 40 were used, ranging from 34.2 inches for avessel/shell 40 of 3.0 inch nominal diameter, to 260 inches for a vessel40 of 10.0 inch nominal diameter.

Various lengths of pipe member 24 were used, ranging from approximately7.30 inches for a pipe member 24 of 3.0 inches nominal diameter, to 12.0inches for all pipe member diameters of approximately 1.0 inches nominaldiameter and greater.

Water at 15° C. and air at 21° C. was used as the liquid and gas,respectively. Water, having bubbles of air of a size greater than 100microns therein the majority of which were of a range of size betweenabout 100 μm to 3 mm, and under a pressure slightly exceeding 20 psig,was provided to pipe member 24, and sprayed into an upper portion ofvessel 40 via rectangular slots 90, such upper portion of the vesselcontaining gas, under a pressure of approximately 20 psig, which usesslightly less than the supplied pressure due to the pressure drop acrossthe aperture(s), and a lower portion of said vessel containing waterhaving microbubbles therein.

Four inlet flow rates of water were used, namely 6 ft./sec, 7 ft./sec, 8ft./sec., and 9 ft./sec into the vessel 40 via pipe member 24. A lowerwithdrawal pipe was used to withdraw water having microbubbles entrainedtherein from vessel 40, which was then provided in a holding tank (notshown) at ambient atmospheric pressure.

In all seventeen instances for the devices tested, microbubbles wereformed in vessel 40 over each of the four volumetric flow rates, ofdimensions less than 100 microns.

EXAMPLE 2

Purpose

The purpose of this experiment was to confirm various formula foroptimum creation of microbubbles using the apparati of the presentinvention.

This was done by evaluating the effect of aperture size and aperturesexit area on the size of the bubbles produced.

Apparatus

Apparatus of the type shown in FIG. 14 was selected, and in particularan apparatus of FIG. 14 having the dimensions for inlet pipe member ODand ID and (upper) impaction pipe length, as well as shell (vessel)height and diameter.

FIG. 15 shows associated equipment used with the selected model ofapparatus 10 of the present invention in conducting the above tests APlexiglas receiving tank 100 was utilized for receiving water havingmicrobubbles entrained therein from apparatus 10 and to permitobservation of bubble rise to permit calculation of bubble velocity(used to determine bubble size). A ruler 102 was attached to the outsideof the tank to allow form measuring distance travelled by bubbles per agiven time interval, to calculate (in the manner described below) thebubble size. A separate tank 104 was provided as a reservoir to permitsupply of water to pump 106. Additional piping 108 permitted supply, viaa globe valve 110 and venturi nozzle 112 to pipe member 24 of apparatus10. Water exiting vessel 40 of apparatus 10 passed through a flow meter115 and pressure gauge 117, and then through a globe valve 118 toPlexiglas tank 100.

Procedure

Pipe members 24 were created, having horizontally-extending cylindricalapertures 32, of diameter, number, and combined exit area Ae as recordedin FIG. 16.

Each combination of hole (aperture) size and exit area was tested withthe same standard procedure set out below. Each test was run under thesame conditions of back pressure (i.e. pressure of gas in the upperportion of vessel 40, namely approximately 20 psi), flow rate, watervolume, water temperature, and pressure drop across the Venturi nozzle.The same apparatus 10 was used for all the tests, and pipe member 24 waschanged between runs.

Measuring the rise of the bubbles against time permitted determinationthe size of the average bubble in the tank.

-   -   The apparatus 10 was connected to the Plexiglas pump 100 and        pump 106;    -   Valve 118 from tank 100 was opened to allow equilibrium level        between tank 100 and vessel 40 of apparatus 10;    -   Pump 106 was started and allowed to run until constant level was        achieved in vessel 40 of apparatus 10;    -   Valve 110 controlling flow through venturi nozzle 112 was        adjusted to create a 20 psi drop across the nozzle 112;    -   The back pressure on vessel 40, namely the pressure of the gas        in upper portion of vessel 40, was then adjusted to 20 psi;    -   The apparati 10 and test equipment was left to run for 3.5        minutes;    -   Pump 106 was turned off and valve 118 between vessel 40 and tank        100 was closed;    -   Once a clear view at the bottom to the rear of the tank 100 was        established bubble rise was monitored and recorded at the given        time intervals;    -   Once tank 100 became clear of bubbles the top of vessel 40 was        removed and pipe member 24 was changed to a pipe member having        differing number and/or diameter of apertures;

The above procedure was repeated for pipe members 24 having apertures 32of various number and/or diameter, to determine the effect of area andhole size on the vessel's performance.

The results of the measurements, and resulting calculations, arecompiled in Table 16.

Calculations

The design uses the formula: $\begin{matrix}{A_{i} = \frac{\pi \times D_{i}^{2}}{4}} & {{Eqn}.\quad 1}\end{matrix}$

where: A_(i)=inlet area

-   -   D_(i)=inside diameter of pipe

This formula defines the inlet area of pipe on the vessel 40. The inletarea Ai is used to determine the gap size or maximum hole dimension.$\begin{matrix}{{Gap} = \frac{A_{i}}{\pi \times D_{o}}} & {{Eqn}.\quad 2}\end{matrix}$

where: Gap=hole dimension or Gap size

-   -   A_(i)=inlet area    -   D_(o)=outside diameter of pipe

This formula defines the maximum length of one of the holes' dimensions.The maximum combined aperture exit area Ae is determined using thepipes' dimensions in the following formula:A _(e) =D _(i)×π×Gap  Eqn. 3

combining equations #1, #2, and #3 results in:$A_{e} = \frac{\pi \times D_{i}^{3}}{4^{\prime}D_{o}}$

where: A_(e)=maximum exit area

-   -   Di=inside diameter of pipe    -   Do=outside diameter of pipe

This formula defines the maximum area that will produce the desiredmicrobubbles. Exit areas less than this value are capable of producingthe microbubbles whereas any area greater than this does not producebubbles that are sufficiently small. Both the hole size and exit areaare parameters that effect the size of the bubbles that are produced bythe vessel.

Using Stoke's Law the size of the bubbles produced is determined by therise velocity of these bubbles. Stokes Law states: $\begin{matrix}{v = \frac{g\quad\left( {\rho_{w} - \rho_{a}} \right)\quad D^{2}}{18\mu}} & {{Eqn}.\quad 4}\end{matrix}$

where:

-   -   v=velocity of bubble rise    -   g=gravitational constant    -   ρ_(w), ρ_(a)=density of wafer and air    -   μ=viscosity of fluid    -   D=diameter of gas bubble in fluid

Each of the experimental runs produced data which appear in FIG. 16.Each experimental run is also accompanied by a corresponding holediameter, number of holes and exit area.

Time and distance traveled were used to calculate the rise velocity.$\begin{matrix}{v = \frac{d_{2} - d_{1}}{t_{2} - t_{1}}} & {{Eqn}.\quad 5}\end{matrix}$with the following units v—mm/s

-   -   d—mm    -   t—sec.

The rise velocity from each interval was used to calculate thecorresponding bubble diameter using a form of Stoke's Law:$\begin{matrix}{D = \sqrt{\frac{18\quad v \times \mu}{g\quad\left( {\rho_{w} - \rho_{a}} \right)}}} & {{Eqn}.\quad 6}\end{matrix}$

where

-   -   D=diameter (cm)    -   v=velocity (cm/s)    -   μ=viscosity of water (Poise)=0.0112 P    -   g=gravitational constant=981 cm/s²    -   ρ_(w)=density of water=0.99913 g/cm³@15° C.    -   ρ_(a)=density of air=1.239 mg/cm³@15° C.

The number of holes, the hole diameter and the resulting exit area weredetermined using the following equation. $\begin{matrix}{A_{e} = {{NH}*D_{A}^{2}\frac{\pi}{4}}} & {{Eqn}.\quad 7}\end{matrix}$

where: A_(e)=exit area

-   -   NH=number of holes πDi²    -   D_(A)=hole diameter        Sample Calculations

The first calculation needed was to determine the maximum exit areaD_(i) = 0.824 D_(o) = 1.05$A_{e} = \frac{\pi \times D_{i}^{3}}{4 \times D_{0}}$A_(c) = 0.418487_(in²)

The following calculations are those used to determine the exit area ata given hole size and number.${{NH} = 21};{{Dia} = {{{5/32^{''}}\quad A_{e}} = {{{NHxD}_{A}^{2}\frac{x\quad\underset{\_}{\pi}}{4}A_{e}} = 0.4026_{{in}^{2}}}}}$

The following are a set of sample calculations for one interval. Thecalculations find the rise velocity of the bubbles and theircorresponding diameters.${d_{2} = 4};{d_{1} = 3};{t_{1} = 5};{t_{2} = 10};{v = \frac{d_{2} - d_{1}}{t_{2} - t_{1}}};$v = 0.2μ  m/s D = 0.00202948  cmResults

Results of the above tests are found in FIG. 16. FIG. 16 lists the drillsizes used for creating the apertures, the number of holes (apertures),and the corresponding combined exit area Ae for each pipe member(nozzle) 24, as well as the resulting bubble size.

As may be seen from FIG. 16, where the combined exit area Ae of theapertures exceeded the pre-determined exit area of Ai×Di/Do, namelyexceeded 0.418487 in², the bubble size was greater than 50 microns.(ref. those tests where bubble diameter was 68.26, 53.2, 68.45, 53.6,58.71, 65.60 and 82.44 μm respectively).

As may also be seen from FIG. 16, where the aperture diameter wasgreater than Ai/(outer circumference of pipe member 24), namely greaterthan 0.161 inches, the average bubble size was greater than 50 microns.

Where the combined aperture exit area Ae was less than or approximatelyequal to Ai×Di/Do, namely less than or equal to 0.418487 in² and theaperture diameter less than or equal to Ai/(outer circumference of pipemember 24), bubble size was less than 50 microns.

FIG. 17 is a graph prepared from that illustrates a relationship betweencombined exit area Ae and bubble diameter. The average diameter from thefirst 30 seconds (in most cases) was plotted against the exit area. FIG.17 demonstrates a defined relationship between the two variables thatoccurs while the hole diameter is held constant. This gives evidence ofthe influence of exit area on bubble size. The larger the exit area thelarger the size of the bubbles produced.

FIG. 17 has an area that is below and to the right of the dotted line.Such represents a design configuration of the apparatus 10 of thepresent invention which produces microbubbles in the desired range ofless than 50 microns.

Although the disclosure describes and illustrates selected embodimentsof the invention, it is to be understood that the invention is notlimited to these particular selected embodiments. Many variations andmodifications will now occur to those skilled in the art. For a completedefinition of the scope of the invention, reference is to further be hadto the summary of the invention and in particular the appended claims.

1. An apparatus having means for creating microbubbles in a liquid topermit a selected gas to better react with impurities entrained in saidliquid, comprising: means for introducing gas bubbles, the majority ofwhich are of a size greater than 100 microns, into a liquid to form aliquid-gas mixture; elongate, hollow pipe means, substantiallysymmetrical in cross-section of interior cross-sectional area Ai,positioned substantially vertically, adapted to receive said liquid-gasmixture and supply said liquid-gas mixture under a first pressure toaperture means, said pipe means having plug means situate at a lowermostdistal end thereof for preventing egress of liquid vertically downwardfrom said distal end; said aperture means situate on said pipe means anddisposed substantially perpendicular to a longitudinal axis of said pipemeans and extending from an interior of said pipe means to an exteriorof said pipe means, adapted to direct said liquid substantiallyhorizontally outwardly from said pipe means; and said pipe means ofuniform wall thickness and having a maximum interior width D_(i) and amaximum exterior width D_(o), having identical moments of inertia aboutat least two separate axis in a cross-sectional plane through said pipemeans; said aperture means comprising at least one or more apertureshaving a combined cross-sectional exit area A_(e); and said combinedaperture exit area A_(e) defined as a function of widths D_(i) and D_(o)and said cross-sectional area A_(i) of said pipe means, wherein A_(e) isno greater than:A_(i)×D_(i)/D_(o)
 2. The apparatus as claimed in claim 1, wherein saidaperture means comprises a single aperture, and the individual area ofsaid single aperture is not greater than A₁×D_(i)/2D_(o)
 3. Theapparatus as claimed in claim 1, wherein said aperture means comprisesat least one aperture, and wherein the individual cross-sectional areaof each of said at least one aperture is no greater thanA_(i)×D_(i)/2D_(o).
 4. The apparatus as claimed in claim 1, 2, or 3,further comprising: a containment vessel, an upper portion adapted tocontain quantities of said gas at a second pressure greater than ambientpressure but less than said first pressure, a lower portion adapted tocapture said liquid-gas mixture having microbubbles of gas entrainedtherein and to permit said microbubbles to react with said entrainedimpurities; and said second pressure being at least 10 psi greater thansaid ambient pressure.
 5. An apparatus for creating microbubbles of gasin a liquid, comprising: a vessel adapted to be positioned substantiallyvertically and adapted to contain a volume of gas in an upper portionthereof under a second pressure exceeding ambient by at least 10 psi;elongate, hollow pipe means for providing said liquid to an interior ofsaid vessel, having a longitudinal axis and substantially symmetrical incross-section so as to have identical moments of inertia about at leasttwo separate axis in a cross-sectional plane through said pipe means, ofuniform wall thickness, and having a maximum interior width D_(i) and amaximum exterior width D_(o) and an interior cross-sectional area A_(i),said pipe means situated in said vessel and proximate said upper portionof said vessel and extending substantially vertically downwardly withinsaid vessel, adapted for supplying a liquid under a first pressuregreater than said second pressure to an interior of said vessel, andhaving plug means situate at a distal end thereof for preventing egressof liquid vertically downward from said distal end; at least twoapertures situate in said pipe means and disposed substantiallyperpendicular to a longitudinal axis of said pipe means, each extendingfrom an interior of said pipe means to an exterior of said pipe means,each adapted to direct said liquid substantially horizontally outwardlyfrom said pipe means, of combined cross-sectional exit area A_(e); andsaid combined aperture exit area A_(e) of said apertures defined as afunction of widths D_(i) and D_(o) and said cross-sectional area A_(i)of said pipe means, wherein A_(e) is no greater than:A _(i)×D_(i)/D_(o) and where the individual cross-sectional area of eachaperture is no greater than A_(i)×D_(i)/2D_(o).
 6. The apparatus asclaimed in claim 5, further comprising: a containment vessel, an upperportion adapted to contain quantities of said gas at a second pressuregreater than ambient pressure but less than said first pressure, a lowerportion adapted to capture said liquid-gas mixture having microbubblesof gas entrained therein and to permit said microbubbles to react withsaid entrained impurities; and said second pressure being at least 10psi greater than said ambient pressure.
 7. The apparatus as claimed inclaim 1, 3, or 6, said aperture means having a maximum verticaldimension G, said pipe means having an exterior circumference C, whereinG is no greater than A_(i)/C.
 8. The apparatus as claimed in claim 1, 3,or 6 wherein said aperture means comprise substantially cylindricalaperture means.
 9. The apparatus as in claim 1, 3, or 6, said pipe meanshaving an exterior circumference C, wherein said apertures comprisecylindrical apertures each of diameter D_(A), where D_(A) is less thanA_(i)/C.
 10. The apparatus as claimed in claim 1, 3, or 6, said pipemeans having an exterior circumference C, wherein said aperturescomprise cylindrical apertures each of diameter D_(A), where D_(A) issubstantially equal to A_(i)/C.
 11. The apparatus as claimed in claim 1,3, or 6, wherein said apertures comprise a plurality ofhorizontally-extending slots in said pipe means.
 12. The apparatus asclaimed in claim 1, 3, or 6, said pipe means having an exteriorcircumference C, wherein said apertures comprise a plurality ofhorizontally-extending rectangular slots in said pipe means, each of ahorizontal width no greater than said maximum interior width D_(i) ofsaid pipe means, and each of a vertical depth no greater than A_(i)/C.13. The apparatus as claimed in claim 1, 3, or 6, wherein said aperturescomprise horizontally-extending rectangular slots in said pipe means,each of a width substantially equal to said maximum interior width D_(i)of said pipe means, and of a vertical depth substantially equal toA_(i)/C.
 14. The apparatus as claimed in claim 1, 3, or 6, wherein saidapertures comprise a plurality of vertically-extending slots in saidpipe means.
 15. The apparatus as claimed in claim 1, 3, or 6, whereinsaid apertures comprise vertically-extending slots in said pipe means,said pipe means having an exterior circumference C, wherein saidapertures are of a width no greater than A_(i)/C.
 16. The apparatus asclaimed in claim 1, 3, or 6, wherein said apertures comprise a pair ofvertically-extending slots in said pipe means, disposed on substantiallymutually-opposite sides of said pipe means, said pipe means having anexterior circumference C, wherein said apertures are of a width nogreater than A_(i)/C.
 17. The apparatus as claimed in claim 6 whereinsaid pipe means comprises a substantially cylindrical pipe member havingan exterior circumference C, said maximum interior width D_(i) equal toan inner diameter of said pipe member, and said maximum exterior widthD_(o) equal to an outer diameter of said pipe member.
 18. The apparatusas claimed in claim 17, wherein said apertures comprise substantiallycylindrical apertures.
 19. The apparatus as claimed in claim 17, whereinsaid apertures comprise substantially cylindrical apertures, each havinga diameter no greater than A_(i)/C.
 20. The apparatus as claimed inclaim 17, wherein said apertures comprise cylindrical apertures each ofdiameter D_(A), where D_(A) is substantially equal to A_(i)/C.
 21. Theapparatus as claimed in claim 17, wherein said apertures comprise atleast a pair of horizontally-extending slots in said pipe member. 22.The apparatus as claimed in claim 17, wherein said apertures comprisehorizontally-extending rectangular slots in said pipe member, and eachof a vertical depth equal to or less than A_(i)/C.
 23. The apparatus asclaimed in claim 22, wherein said horizontally-extending slots eachextend to a depth within said pipe member substantially equal to ½D_(o),and are of a horizontal width substantially equal to D_(o).
 24. Theapparatus as claimed in claim 17 wherein said apertures comprise atleast a pair of vertically-extending slots in said pipe member.
 25. Theapparatus as claimed in claim 17, wherein said apertures comprisevertically-extending slots in said pipe member, each extendingvertically along said pipe member a distance no greater than A_(i)/C .26. The apparatus as claimed in claim 17, wherein said aperturescomprise vertically-extending rectangular slots in said pipe member,each of a width substantially equal or less than A_(i)/C.
 27. Theapparatus as claimed in claim 5, wherein said pipe means comprises asubstantially square pipe member of substantially square exterior andinterior dimensions, having an exterior circumference C, said maximuminterior width D_(i) equal to a length of an inner side width of saidsquare pipe member, and said maximum exterior width D_(o) equal to alength of an outer side width of said square pipe member.
 28. Theapparatus as claimed in claim 27, wherein said apertures comprisecylindrical apertures.
 29. The apparatus as claimed in claim 27, whereinsaid apertures comprise cylindrical apertures, each having a diameter nogreater than A_(i)/C.
 30. The apparatus as claimed in claim 27, whereinsaid apertures comprise cylindrical apertures each of diametersubstantially equal to A_(i)/C.
 31. The apparatus as claimed in claim27, wherein said apertures comprise at least a pair ofhorizontally-extending slots in said pipe member.
 32. The apparatus asclaimed in claim 27, wherein said apertures comprisehorizontally-extending rectangular slots in said pipe member, each of awidth substantially equal to said maximum interior width D_(i) of saidpipe member, and each of a vertical depth equal to or less than A_(i)/C.33. The apparatus as claimed in claim 27, wherein said aperturescomprise at least a pair of vertically-extending slots in said pipemember.
 34. The apparatus as claimed in claim 27, wherein said aperturescomprise vertically-extending slots in said pipe member, each of a widthsubstantially equal or less than A_(i)/C.
 35. The apparatus as claimedin claim 27, wherein said apertures comprise vertically-extendingrectangular slots in said pipe member, and each of a vertical lengthsubstantially equal to said maximum interior width D_(i).
 36. Theapparatus as claimed in claim 5, wherein a cross-section of said pipemeans comprises a substantially equilateral triangle of substantiallyequilateral triangular exterior and interior cross-section, maximuminterior width D_(i) comprising a length of a side of the said interiorcross-section, maximum exterior width Do comprising a length of a sideof said exterior cross-section, and having an exterior circumference C.37. The apparatus as claimed in claim 36, wherein said aperturescomprise cylindrical apertures.
 38. The apparatus as claimed in claim36, wherein said apertures comprise cylindrical apertures, each having adiameter no greater than A_(i)/C.
 39. The apparatus as claimed in claim36, wherein said apertures comprise cylindrical apertures each ofdiameter substantially equal to A_(i)/C.
 40. The apparatus as claimed inclaim 36, wherein said apertures comprise at least a pair ofhorizontally-extending slots in said pipe member.
 41. The apparatus asclaimed in claim 36, wherein said apertures comprisehorizontally-extending rectangular slots in said pipe member, each of awidth substantially equal to said maximum interior width D_(i) of saidpipe member, and each of a vertical depth equal to or less than A_(i)/C.42. The apparatus as claimed in claim 36, wherein said aperturescomprise at least a pair of vertically-extending slots in said pipemember.
 43. The apparatus as claimed in claim 36, wherein said aperturescomprise vertically-extending slots in said pipe member, each of a widthsubstantially equal or less than A_(i)/C.
 44. The apparatus as claimedin claim 36, wherein said apertures comprise vertically-extendingrectangular slots in said pipe member, and each of a vertical lengthsubstantially equal to said maximum interior width D_(i).
 45. Theapparatus as claimed in claim 1 wherein said apertures are situate insaid plug means.
 46. The apparatus as claimed in claim 19 wherein saidapertures comprise a plurality ‘n’ number of circular apertures ofdiameter Da, wherein n is substantially equal to:A_(e)(π×Da²/4)
 47. The apparatus as claimed in claim 20 wherein saidapertures comprise a plurality n number of circular apertures, wherein nis function of Di and Do, wherein n=nearest whole integer to[16×D_(o)/D_(i)]
 48. An apparatus for creating microbubbles of gas in aliquid in the approximate size range of 5 to 100 μm, comprising: acontainment vessel having a substantially longitudinal axis adapted tobe positioned vertically and contain a volume of gas in an upper portionthereof under a second pressure of at least 20 psig; elongate, hollowpipe means, having a longitudinal axis and substantially symmetrical incross-section so as to have identical moments of inertia about at leasttwo axis in a cross-sectional plane through said pipe means, ofsubstantially uniform wall thickness, having a maximum interior widthD_(i) and a maximum exterior width D_(o) and a cross-sectional areaA_(i), said pipe means situate substantially centrally in saidcontainment vessel and proximate a top end of said containment vesseland extending substantially vertically downwardly within said vessel,adapted for supplying a liquid having bubbles of gas entrained thereinunder a first pressure greater than said second pressure to an interiorof said vessel via a plurality of apertures, and having plug meanssituate at a distal end thereof for preventing egress of liquidvertically downward from said distal end; said apertures disposed in oneor more planes each substantially perpendicular to a longitudinal axisof said pipe means and each extending from an interior of said pipemeans to an exterior of said pipe means, each adapted to direct saidliquid horizontally outwardly from said conduit means into said vessel,of combined cross-sectional exit area A_(e); and said combined exit areaA_(e) of said apertures defined as a function of widths D_(i) and D_(o)and the interior cross-sectional area A_(i) of said pipe means, whereinA_(e) substantially equal to:A_(i)×D_(i)/D_(o) and where the individual cross-sectional area of eachaperture is no greater than A_(i)×D_(i)/2D_(o).
 49. The apparatus asclaimed in claim 48, said apertures each having a maximum verticaldimension G, said pipe means having an exterior circumference C, whereinG is no greater than A_(i)/C.
 50. The apparatus as claimed in claim 49,further comprising a baffle member situate in said vessel, immediatelybelow said plug means of said pipe member, adapted to allow liquidejected from said apertures to pass therethrough and thereafter to abottom portion of said vessel.
 51. A method for creating microbubbles ofgas in a liquid having matter entrained in such liquid and exposing saidmicrobubbles to said matter, comprising: providing gas to said liquid toform a gas/liquid mixture; directing said gas-liquid mixture into ahollow pipe member, said pipe member having a maximum interior widthD_(i) and a maximum exterior width D_(o) and plug means situate at alowermost distal end thereof for preventing egress of liquid verticallydownward from said distal end, said pipe member situate proximate anupper portion of a containment vessel and extending into an interior ofsaid containment vessel, said upper portion of said containment vesselcontaining said gas being under a second pressure of at least 10 psi,and a bottom portion of said containment vessel substantially containingsaid liquid; injecting said gas-liquid mixture under a first pressureexceeding said second pressure via said pipe member, into saidcontainment vessel; spraying substantially radially outwardly from saidpipe member said gas-liquid mixture into said upper portion of saidcontainment vessel via at least two apertures in said pipe member; saidat least two apertures in said pipe member in communication with saidgas-liquid mixture in said pipe member and having a combined area A_(e)sized as a function of a maximum interior widths D_(i) and maximumoutside width D_(o) and a cross-sectional area A_(i) of said pipemember, wherein A_(e) is substantially equal to:A_(i)×D_(i)/D_(o) and where the individual cross-sectional area of eachaperture is no greater than A_(i)×D_(i)/2D_(o); and removing from saidcontainment vessel said liquid which has been exposed to saidmicrobubbles.
 52. The method as claimed in claim 51 further adapted toallow purification of said liquid by allowing said microbubbles entainedin said liquid to react with said liquid and/or contaminants therein insaid bottom portion of said vessel, further comprising the step ofcontaining within said bottom portion of said vessel said liquid withmicrobubbles entrained therein and withdrawing said liquid from saidbottom portion of said vessel at a rate approximately equal to a rate atwhich said liquid is introduced into said containment vessel via saidpipe member.
 53. The method as claimed in claim 52, wherein said rate ofwithdrawing said from the bottom portion of said vessel is substantiallyat a rate which microbubbles entrained in said liquid rise in saidvessel, so that at a time when liquid is removed from said bottomportion of said vessel said microbubbles will have travelled upwardly adistance through said liquid substantially equal to a majority of adepth of liquid in said bottom portion of said vessel.
 54. The method asclaimed in claim 51, further comprising the step of passing saidgas-liquid mixture sprayed from said pipe member through a baffle platemember positioned in said containment vessel below said pipe member andintermediate said upper portion and said bottom portion of saidcontainment vessel, and adjusting the rate of injection and removal ofgas-liquid from the vessel so that baffle plate member is positionedabove the level of the liquid in the vessel.
 55. The method as claimedin claim 51, further comprising the method of maintaining the pressureof the vessel in the upper portion thereof at a pressure of at least 15psig.
 56. The method as claimed in claim 51, said step of sprayingsubstantially radially outwardly said gas-liquid mixture into said upperportion of said containment vessel via at said apertures furthercomprising spraying said gas-liquid mixture against sides of thecontainment vessel.
 57. A method for converting a liquid-gas mixturehaving bubbles of gas therein the majority of which are greater than 100microns in size to a liquid-gas mixture having microbubbles of gastherein the majority of which are of a size between 5-100 microns atstandard temperature and pressure, comprising the steps of: directingsaid gas-liquid mixture having bubbles of gas therein the majority ofwhich are greater than 100 microns in size into a hollow pipe member,said pipe member being substantially symmetrical in cross-section andhaving identical moments of inertia about at least two axis in a planeof cross-section through said pipe, of uniform thickness, having amaximum interior width D_(i) and a maximum exterior width D_(o) furtherhaving plug means situate at a lowermost distal end thereof forpreventing egress of liquid vertically downward from said distal end,said pipe situate proximate an upper portion of a containment vessel andextending into an interior of said containment vessel, said upperportion of said containment vessel containing said gas being under asecond pressure of at least 15 psig; injecting said gas-liquid mixture,under a pressure of at least 5 psig higher than said gas in saidcontainment vessel, into said vessel via said pipe member, spraying saidgas-liquid mixture substantially radially outwardly from said pipemember into said containment vessel via a plurality of apertures in saidpipe member, so that said gas-liquid mixture contacts interior sides ofsaid vessel; said plurality of apertures in said pipe member incommunication with said gas-liquid mixture in said pipe member andhaving a combined area A_(e), said apertures sized as a function of saidmaximum interior width D_(i) and said maximum outside width D_(o) and across-sectional area A_(i) of said pipe member, wherein A_(e) issubstantially equal to:A_(i)×D_(i)/D_(o) and where the individual cross-sectional area of eachaperture is no greater than A_(i)×D_(i)/2D_(o)
 58. The method as claimedin claim 57, wherein said step of spraying said liquid/gas mixture intosaid containment vessel via said apertures is carried out by apertureseach having a maximum vertical dimension G, said pipe means having anexterior circumference C, wherein G is no greater than A_(i)/C.
 59. Themethod as claimed in claim 58, said vessel further having a bottomportion adapted for containing, for a time, said gas-liquid mixturehaving microbubbles of gas entrained therein, said method furthercomprising the step of removing from said bottom portion of saidcontainment vessel said liquid having microbubbles of gas entrainedtherein at a rate substantially equal to the rate at which said liquidis supplied to such vessel
 60. The method as claimed in claim 59,wherein said rate of withdrawing said liquid having gas bubblesentrained therein from the bottom of said vessel is substantially at arate which microbubbles entrained in said liquid rise in said vessel, sothat at a time when liquid with entrained microbubbles is removed fromsaid bottom of said vessel said microbubbles will have travelledupwardly a distance through said liquid equal to a depth of liquid insaid bottom of said vessel.
 61. The method as claimed in claim 57wherein said gas is air.
 62. A method for converting a liquid-gasmixture having bubbles of gas therein the majority of which are greaterthan 100 microns in average size to a liquid-gas mixture havingmicrobubbles of gas therein the majority of which are of an average sizebetween 5-100 microns at standard temperature and pressure, comprisingthe steps of: directing said gas-liquid mixture having bubbles of gastherein the majority of which are greater than 100 microns in size intoa hollow, substantially vertical pipe member, having a maximum interiorwidth D_(i) and a maximum exterior width D_(o), said pipe member havingplug means situate at a lowermost distal end thereof for preventingegress of liquid vertically downward from said distal end; spraying saidgas-liquid mixture substantially radially outwardly from said pipemember via a plurality of apertures in said pipe member, so that saidgas-liquid mixture contacts a vertically extending surface; saidplurality of apertures in said pipe member in communication with saidgas-liquid mixture in said pipe member and having a combined area A_(e),said apertures sized as a function of said maximum interior width D_(i)and said maximum outside width D_(o) and a cross-sectional area A_(i) ofsaid pipe member, wherein A_(e) is no greater than:A_(i)×D_(i)/D_(o) and where the individual cross-sectional area of eachaperture is no greater than A_(i)×D_(i)/2D_(o); collecting a resultinggas-liquid mixture having microbubbles of gas entrained therein in avessel, under a pressure of at least 10 psig; and removing saidgas-liquid mixture from said vessel.
 63. A method for continuouslypurifying a liquid containing impurities by exposing said liquid andimpurities for a time in a substantially vertical containment vessel tomicrobubbles of gas in the range of 5 to 100 microns in diameter,comprising the steps of: directing a gas-liquid mixture containingimpurities and bubbles of gas the majority of which are in excess of 100microns in diameter into a hollow pipe member, said pipe member ofuniform thickness and having a maximum interior width Di and a maximumexterior width Do and identical moments of inertia on two axis in aplane of cross-section through said pipe means, further having plugmeans situate at a lowermost distal end thereof for preventing egress ofliquid vertically downward from said distal end, said pipe means situateproximate an upper portion of said containment vessel and extendingvertically downwardly in an interior of said containment vessel, saidupper portion of said containment vessel containing said gas, and beingunder pressure of at least 15 psig; injecting said gas-liquid mixture,under a pressure of at least 5 psig higher than said gas in saidcontainment vessel, into said vessel via said pipe member; spraying saidgas-liquid mixture substantially horizontally outwardly from said pipemember into said upper portion of said containment vessel via aplurality of apertures in said pipe member so that said gas-liquidmixture contacts interior sides of said vessel; said plurality ofapertures in said pipe member in communication with said gas-liquidmixture in said pipe member and having a combined area A_(e), saidapertures sized as a function of said maximum interior width D_(i) andsaid maximum outside width D_(o) and a cross-sectional area A_(i) ofsaid pipe member, wherein A_(e) is no greater than:A_(i)×D_(i)/D_(o) and where the individual cross-sectional area of eachaperture is no greater than A_(i)×D_(i)/2D_(o); collecting saidgas-liquid mixture, now having microbubbles of gas entrained therein themajority of which are now of a size less than 100 microns in diameter,in a bottom portion of said containment vessel; removing, from saidbottom portion of said vessel, said liquid with gas microbubblesentrained therein at a rate which said microbubbles entrained in saidliquid rise in said vessel so as to permit said gas microbubbles time toreact with impurities in said liquid; and supplying said liquid-gasmixture to said pipe member substantially at a rate at which saidliquid-gas mixture having gas microbubbles entrained therein is removedfrom the bottom of said vessel.
 64. The method as claimed in claim 63,wherein said step of spraying said liquid-gas mixture into saidcontainment vessel via said apertures is carried out by apertures eachhaving a maximum vertical dimension G, said pipe means having anexterior circumference C, wherein G is no greater than Ai/C.
 65. Themethod as claimed in claim 62, 63, or 64, wherein Ae is substantiallyequal to Ai×Di/Do.